Preheat your oven to 375°F (190°C) and lightly grease a medium-sized oven-safe baking dish with the coconut oil.
In a large mixing bowl, whisk together the Greek yogurt, eggs, vanilla extract, sea salt, half of the cinnamon, and half of the maple syrup until the mixture is completely smooth.
Core and dice the apples into uniform half-inch pieces.
In a separate small bowl, toss the diced apples with the remaining cinnamon and maple syrup until they are evenly coated.
Pour the yogurt base into the prepared baking dish, smoothing the top with a spatula.
Scatter the cinnamon-spiced apple pieces evenly across the top of the yogurt mixture.
Bake for 25 to 30 minutes until the yogurt is set around the edges and the apples are tender and fragrant.
Remove from the oven and let the dish rest for 5 to 10 minutes to allow the custard to firm up before slicing into two generous portions.